1. Field of the Invention
The present invention relates to an organic light emitting display and method, and more particularly, to an organic light emitting display providing an ultraviolet ray protection function and method of manufacturing the same.
2. Description of the Related Art
Generally, organic light emitting displays include organic light emitting diodes (“OLEDs”) deposited on thin film transistors (“TFTs”) of an electric circuit so that a light emitting layer of a selected OLED emits light in response to a signal controlled by the TFT.
FIG. 1 shows the typical structure of such an organic light emitting display. As described above, a TFT 12 as a driving unit and an OLED 13 as a light emitting unit are deposited between a lower substrate 11 and an upper substrate 15.
The OLED 13 includes an anode 13a, a light emitting layer 13b and a cathode 13c, which are sequentially deposited upon one another, and is segmented into a matrix of pixels by bank portions 13d. In the case of a color device, the regions segmented by the bank portions 13d are subpixels producing red (R), green (G) and blue (B) light, respectively, and one color pixel consists of these 3 sub-pixels.
Reference numeral 12a denotes an insulating layer. Reference numeral 14 denotes an encapsulation layer that prevents the penetration of moisture and oxygen into the OLED 13 and has a structure including a plurality of organic layers 14a and inorganic layers 14b which are alternately deposited with respect to each other. In other words, an inorganic layer 14b is interposed between two organic layers 14a. The inorganic layer 14b, composed of, for example, a ceramic, primarily plays a role of preventing the penetration of oxygen and moisture, and the organic layer 14a primarily performs the function of providing flexibility.
The region where the OLEDs 13 are arranged is called a display area A1, which corresponds to an area where an image is displayed, and the outer border region in which the OLEDs 13 are not arranged is called a non-display area A2. When binding an upper substrate 15 to the device, an ultraviolet ray (“UV”) sealing adhesive 16 is applied to the non-display area A2 and cured. That is, after applying the UV sealing adhesive 16 to the non-display area A2 and putting the upper substrate 15 on the encapsulation layer 14, ultraviolet rays are radiated for a predetermined time onto the UV sealing adhesive 16 for purposes of curing. The upper substrate 15 then binds to the encapsulation layer 14 while the adhesive 16 is hardened. The UV sealing adhesive 16 also functions as a sealing film.
When the OLED 13 or the TFT 12, in addition to the UV sealing adhesive 16, is exposed to UV rays in such a UV curing process, the characteristics of the semiconductor film are degraded. Conventionally, degradation of the semiconductor film is prevented by a method of using a shading mask to cover a region where ultraviolet rays are not to be radiated, that is, where the display region has been adopted. In other words, after forming a shading mask using, for example, quartz, and putting the shading mask on the upper substrate 15 to cover the display region, ultraviolet rays are radiated only onto the UV sealing adhesive 16 to harden the UV adhesive 16.
However, since the separate shading mask has to be prepared, the manufacturing process is very complicated. In addition, the ultraviolet rays can be radiated onto the OLED 13 or the TFT layer 12 when the shading mask is not quite accurately positioned on the upper substrate 15. Accordingly, the processes of both making the shading mask and positioning the shading mask on the upper substrate 15 complicate the UV curing process.
Japanese Patent Publication No. 2004-139767 discloses a structure of applying a hygroscopic agent to a wide area between two substrates, instead of using a shading mask, and thus the hygroscopic agent blocks the ultraviolet rays from traveling to a light emitting unit and a driving unit. However, such a structure is not always possible and is possible only in the case of a so-called can type substrate in which a hollow space accommodating the hygroscopic agent is prepared. Thus, the whole manufacturing process is complicated since a separate process of preparing the hydroscopic agent and an assembly process, in addition to the film formation processes, are required as when using the conventional shading mask.